No abstract

Their nanoscale size endows perovskite quantum dots (QDs) with processing flexibility and high tunability of optoelectronic properties. The vast surface area also provides an opportunity for ligand engineering to offer QDs extra protection, which however, will impede charge transport in the QD array. Currently, the surface treatments that can balance both stability and conductivity of the perovskite QD array remain a huge challenge. Here, we report in situ growth of an atomic guanidinium lead iodide perovskite matrix on CsPbI 3 QDs. In addition to the effect of trap passivation, the matrix can also provide substantial surface strain to improve the QD phase stability. Meanwhile, the ultrathin matrix allows efficient coupling and charge transport in the QD solids. As a result, the CsPbI 3 QD solar cells can achieve both superior device stability and performance. We believe the development of a multifunctional surface matrix will become one of the future research focuses in perovskite QD-based devices.

With outstanding photoelectric properties, organic–inorganic perovskites have become promising materials in the application of solar cells. However, their low stability limits their high conversion efficiency. On the basis of first-principles calculations, we screened out the optimal dopant into MAPbI3 from a variety of organic cations, and further revealed the mechanism underneath for the improved stability of cations doping. Our results have demonstrated that the doping of large-size cations (i.e., IPA+, TriMA+, and GA+) could efficiently inhibit the formation and diffusion of structural defects with high defect formation energies and large migration barriers, which is associated with the lattice expansion and greater hydrogen-bond formation. Our theoretical findings address crucial guidelines to design and synthesize the organic–inorganic perovskite materials with high stability, and provide valuable insights in understanding the stability mechanism, which may enhance the photovoltaic efficiency of perovskite materials and extend their wide applications.